This is fairly simple and easy and should work from most people out there:
In the terminal:
apt-get install flashplugin-nonfree
and then type in:
update-flashplugin-nonfree --install
That’s it. You flash should be working as expected. Go to testing section at the bottom on this post to confirm installation.
In case you tried Choice 1 and failed, try this steps below to install and activate Flash manually.
Launch your browser (I assume IceWeasel?) and download the Flash Player in a separate folder.
At the time of writing this guide the available version was install_flash_player_11_linux.x86_64.tar.gz
Download and save the file in /root directory.
Users should take note that the version used in this guide is x64 which is 64-bit. 32-bit users should choose their versions accordingly.
Download link = http://get.adobe.com/flashplayer/
(Note: Choose Version to download tar.gz for other Linux)
Follow the instructions below:
cd Downloads/ tar xzvf install_flash_player_11_linux.x86_64.tar.gz cp libflashplayer.so /usr/lib/mozilla/plugins/
.
原文：http://www.cnblogs.com/outline/p/flash.html